For the transmission of power, also automatic transmissions, in particular stepped fully automatic transmissions comprising a hydrodynamic torque converter and planetary transmissions are used in the automotive engineering apart from manually shifted change speed transmissions.
Such fully automatic stepped transmissions act as a power shift transmission which work without any interruption of the tractive force, with the power flow occurring via planetary gear sets and the gear changes being established by coupling or releasing individual planetary gear set elements. The process of coupling individual planetary gear set elements is currently performed in most cases by means of multi-disk clutches which have to be designed for a maximum torque to be transmitted and comprise a correspondingly high number of frictional points or disks for torque transmission. Due to the numerous frictional points, the undesired drag torques in the uncoupled state are quite high and have a detrimental effect on the gear efficiency.
For this reason, the generic DE 102 44 523 A1 already proposes a vehicular transmission in which the inner disk support is coupled to a rotatable gearbox component, e.g. a gearbox shaft, via a synchronization. The synchronization selectively allows a decoupling, a frictional or a form-locking coupling of the inner disk supports with the rotatable gearbox component. It is also in the uncoupled state of the synchronization that drag torques occur, but these are much smaller due to the frictional surfaces being substantially smaller as compared to a multi-disk clutch. In the uncoupled state of the gear shift device, i.e. when the multi-disk clutch is opened and the synchronization is uncoupled, a relative rotation occurs due to the lower drag torques exclusively or at least mainly within the area of the synchronization and does not exist at all or scarcely in the area of the multi-disk clutch, so that the gear efficiency is increased.
The construction of the vehicular transmission disclosed in DE 102 44 523 A1, however, is relatively complex due to the large number of individual components as well as three separate springs for axially acting upon these individual components and further comprises an undesirably high gear shift force level.
It is the object of the invention to minimize the number of the individual components and to provide a constructionally simple gear shift device for a motor vehicle transmission, which contributes to a high gear efficiency due to low drag torques.